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38 CB 1.3 GENETIC VARIATION
TRACKING GENES
1. State the possible genotypes of:
(a) a guinea pig with normal hair.
(b) a hairless guinea pig.
(c) a guinea pig that is pure breeding for normal hair.
2. (a) Is hairlessness the dominant condition?
(b) Explain your answer to (a).
3. (a) Complete the Punnett square to show the possible offspring produced when a
pure-breeding guinea pig with normal hair mates with a pure-breeding guinea pig
without hair.
Hairless Guinea Pigs
A rare genetic condition causes some guinea pigs to be born without the ability to produce hair.
The allele carried by most guinea pigs is an (H), which results in normal hair growth. Affected
guinea pigs carry the alleles (hh).
A normal guinea pig A hairless guinea pig
(b) What percentage of the offspring would you expect to have normal hair?
(c) What percentage of the offspring would you expect to be hairless?
(d) What is the expected genotypic ratio of the offspring?
(e) What is the expected phenotypic ratio of the offspring?
Parents’ genotypes: and
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